This invention relates generally to welding of materials, and more particularly to percussive arc welding. More specifically this invention is directed to an improved technique is percussive arc welding a pin member to a base metal.
In percussive arc welding, wherein a pin of some configuration is welded to a base metal, the following sequence of steps is performed by the welding device: the pin to be welded is held by the welding device a given distance from the base metal and an initiating voltage is applied between the pin and the base metal, for the purpose of causing an arc therebetween, the arc establishing a current flow path; after this initiating voltage is applied a capacitive discharge from previously charged capacitors is caused to take place between the pin and the base metal; the capacitive discharge, when following the established arc path between the pin and the base metal is sufficient to cause localized melting of the end of the pin and the region of the base metal around the locus of the termination of the arc; concomitantly with the capacitor discharge the pin is plunged into the base metal, with the melted regions of each joining together and causing a fusion weld.
This technique known as percussive arc welding works very well when all of the steps operate properly. However, it has been observed in many instances surface contaminants of other factors result in poor quality or improper welds due to lack of proper melting of the workpiece. The principal contributing factor to the improper melting was found to be the lack of an arc being established when the voltage was initially applied. The lack of a proper arc at this stage of the process prevented the proper capacitive discharge and consequently prevented proper melting and thus prevented proper welding.